Even if in the vast majority of cases a low number of PD-1+ CD4+ T cells was found in cHL tissues [144], a phase 1 trial of nivolumab showed high and durable responses in 23 heavily pretreated patients with relapsed/refractory disease, indicating that immune checkpoint blockade is an effective treatment approach in cHL [2]. The gene discussed is CD4; the disease is classic Hodgkin lymphoma.